X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=blobdiff_plain;f=src%2Fbin%2Flttng-sessiond%2Fkernel.c;h=4bb418949d3ea330b60397ed2352f5541c7fcbdc;hp=0922c3d490918f3a177a48cecd1b5b94772aa8cb;hb=ccf10263bcd2ca4667b9e1fc4dab64a3c8d8c4d8;hpb=df0f840ba686e3fe670c9906fd46330fff65da07

diff --git a/src/bin/lttng-sessiond/kernel.c b/src/bin/lttng-sessiond/kernel.c
index 0922c3d49..4bb418949 100644
--- a/src/bin/lttng-sessiond/kernel.c
+++ b/src/bin/lttng-sessiond/kernel.c
@@ -1,45 +1,54 @@
 /*
  * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
  *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; only version 2
- * of the License.
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2 only,
+ * as published by the Free Software Foundation.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
 #define _GNU_SOURCE
+#define _LGPL_SOURCE
 #include <errno.h>
 #include <fcntl.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
 #include <unistd.h>
+#include <inttypes.h>
 
 #include <common/common.h>
 #include <common/kernel-ctl/kernel-ctl.h>
+#include <common/kernel-ctl/kernel-ioctl.h>
+#include <common/sessiond-comm/sessiond-comm.h>
 
+#include "consumer.h"
 #include "kernel.h"
+#include "kernel-consumer.h"
 #include "kern-modules.h"
+#include "utils.h"
 
 /*
  * Add context on a kernel channel.
  */
 int kernel_add_channel_context(struct ltt_kernel_channel *chan,
-		struct lttng_kernel_context *ctx)
+		struct ltt_kernel_context *ctx)
 {
 	int ret;
 
+	assert(chan);
+	assert(ctx);
+
 	DBG("Adding context to channel %s", chan->channel->name);
-	ret = kernctl_add_context(chan->fd, ctx);
+	ret = kernctl_add_context(chan->fd, &ctx->ctx);
 	if (ret < 0) {
 		if (errno != EEXIST) {
 			PERROR("add context ioctl");
@@ -50,42 +59,7 @@ int kernel_add_channel_context(struct ltt_kernel_channel *chan,
 		goto error;
 	}
 
-	chan->ctx = zmalloc(sizeof(struct lttng_kernel_context));
-	if (chan->ctx == NULL) {
-		PERROR("zmalloc event context");
-		goto error;
-	}
-
-	memcpy(chan->ctx, ctx, sizeof(struct lttng_kernel_context));
-
-	return 0;
-
-error:
-	return ret;
-}
-
-/*
- * Add context on a kernel event.
- */
-int kernel_add_event_context(struct ltt_kernel_event *event,
-		struct lttng_kernel_context *ctx)
-{
-	int ret;
-
-	DBG("Adding context to event %s", event->event->name);
-	ret = kernctl_add_context(event->fd, ctx);
-	if (ret < 0) {
-		PERROR("add context ioctl");
-		goto error;
-	}
-
-	event->ctx = zmalloc(sizeof(struct lttng_kernel_context));
-	if (event->ctx == NULL) {
-		PERROR("zmalloc event context");
-		goto error;
-	}
-
-	memcpy(event->ctx, ctx, sizeof(struct lttng_kernel_context));
+	cds_list_add_tail(&ctx->list, &chan->ctx_list);
 
 	return 0;
 
@@ -102,8 +76,10 @@ int kernel_create_session(struct ltt_session *session, int tracer_fd)
 	int ret;
 	struct ltt_kernel_session *lks;
 
+	assert(session);
+
 	/* Allocate data structure */
-	lks = trace_kernel_create_session(session->path);
+	lks = trace_kernel_create_session();
 	if (lks == NULL) {
 		ret = -1;
 		goto error;
@@ -123,6 +99,7 @@ int kernel_create_session(struct ltt_session *session, int tracer_fd)
 		PERROR("fcntl session fd");
 	}
 
+	lks->id = session->id;
 	lks->consumer_fds_sent = 0;
 	session->kernel_session = lks;
 
@@ -131,6 +108,9 @@ int kernel_create_session(struct ltt_session *session, int tracer_fd)
 	return 0;
 
 error:
+	if (lks) {
+		trace_kernel_destroy_session(lks);
+	}
 	return ret;
 }
 
@@ -139,17 +119,26 @@ error:
  * kernel session.
  */
 int kernel_create_channel(struct ltt_kernel_session *session,
-		struct lttng_channel *chan, char *path)
+		struct lttng_channel *chan)
 {
 	int ret;
 	struct ltt_kernel_channel *lkc;
 
+	assert(session);
+	assert(chan);
+
 	/* Allocate kernel channel */
-	lkc = trace_kernel_create_channel(chan, path);
+	lkc = trace_kernel_create_channel(chan);
 	if (lkc == NULL) {
 		goto error;
 	}
 
+	DBG3("Kernel create channel %s with attr: %d, %" PRIu64 ", %" PRIu64 ", %u, %u, %d, %d",
+			chan->name, lkc->channel->attr.overwrite,
+			lkc->channel->attr.subbuf_size, lkc->channel->attr.num_subbuf,
+			lkc->channel->attr.switch_timer_interval, lkc->channel->attr.read_timer_interval,
+			lkc->channel->attr.live_timer_interval, lkc->channel->attr.output);
+
 	/* Kernel tracer channel creation */
 	ret = kernctl_create_channel(session->fd, &lkc->channel->attr);
 	if (ret < 0) {
@@ -168,19 +157,24 @@ int kernel_create_channel(struct ltt_kernel_session *session,
 	/* Add channel to session */
 	cds_list_add(&lkc->list, &session->channel_list.head);
 	session->channel_count++;
+	lkc->session = session;
 
-	DBG("Kernel channel %s created (fd: %d and path: %s)",
-			lkc->channel->name, lkc->fd, lkc->pathname);
+	DBG("Kernel channel %s created (fd: %d)", lkc->channel->name, lkc->fd);
 
 	return 0;
 
 error:
+	if (lkc) {
+		free(lkc->channel);
+		free(lkc);
+	}
 	return -1;
 }
 
 /*
  * Create a kernel event, enable it to the kernel tracer and add it to the
  * channel event list of the kernel session.
+ * We own filter_expression and filter.
  */
 int kernel_create_event(struct lttng_event *ev,
 		struct ltt_kernel_channel *channel)
@@ -188,6 +182,9 @@ int kernel_create_event(struct lttng_event *ev,
 	int ret;
 	struct ltt_kernel_event *event;
 
+	assert(ev);
+	assert(channel);
+
 	event = trace_kernel_create_event(ev);
 	if (event == NULL) {
 		ret = -1;
@@ -196,7 +193,16 @@ int kernel_create_event(struct lttng_event *ev,
 
 	ret = kernctl_create_event(channel->fd, event->event);
 	if (ret < 0) {
-		if (errno != EEXIST) {
+		switch (errno) {
+		case EEXIST:
+			break;
+		case ENOSYS:
+			WARN("Event type not implemented");
+			break;
+		case ENOENT:
+			WARN("Event %s not found!", ev->name);
+			break;
+		default:
 			PERROR("create event ioctl");
 		}
 		ret = -errno;
@@ -245,6 +251,8 @@ int kernel_disable_channel(struct ltt_kernel_channel *chan)
 {
 	int ret;
 
+	assert(chan);
+
 	ret = kernctl_disable(chan->fd);
 	if (ret < 0) {
 		PERROR("disable chan ioctl");
@@ -268,6 +276,8 @@ int kernel_enable_channel(struct ltt_kernel_channel *chan)
 {
 	int ret;
 
+	assert(chan);
+
 	ret = kernctl_enable(chan->fd);
 	if (ret < 0 && errno != EEXIST) {
 		PERROR("Enable kernel chan");
@@ -290,9 +300,18 @@ int kernel_enable_event(struct ltt_kernel_event *event)
 {
 	int ret;
 
+	assert(event);
+
 	ret = kernctl_enable(event->fd);
-	if (ret < 0 && errno != EEXIST) {
-		PERROR("enable kernel event");
+	if (ret < 0) {
+		switch (errno) {
+		case EEXIST:
+			ret = LTTNG_ERR_KERN_EVENT_EXIST;
+			break;
+		default:
+			PERROR("enable kernel event");
+			break;
+		}
 		goto error;
 	}
 
@@ -312,9 +331,18 @@ int kernel_disable_event(struct ltt_kernel_event *event)
 {
 	int ret;
 
+	assert(event);
+
 	ret = kernctl_disable(event->fd);
-	if (ret < 0 && errno != EEXIST) {
-		PERROR("disable kernel event");
+	if (ret < 0) {
+		switch (errno) {
+		case EEXIST:
+			ret = LTTNG_ERR_KERN_EVENT_EXIST;
+			break;
+		default:
+			PERROR("disable kernel event");
+			break;
+		}
 		goto error;
 	}
 
@@ -327,17 +355,45 @@ error:
 	return ret;
 }
 
+int kernel_enable_syscall(const char *syscall_name,
+		struct ltt_kernel_channel *channel)
+{
+	return kernctl_enable_syscall(channel->fd, syscall_name);
+}
+
+int kernel_disable_syscall(const char *syscall_name,
+		struct ltt_kernel_channel *channel)
+{
+	return kernctl_disable_syscall(channel->fd, syscall_name);
+}
+
+int kernel_track_pid(struct ltt_kernel_session *session, int pid)
+{
+	DBG("Kernel track PID %d for session id %" PRIu64 ".",
+			pid, session->id);
+	return kernctl_track_pid(session->fd, pid);
+}
+
+int kernel_untrack_pid(struct ltt_kernel_session *session, int pid)
+{
+	DBG("Kernel untrack PID %d for session id %" PRIu64 ".",
+			pid, session->id);
+	return kernctl_untrack_pid(session->fd, pid);
+}
+
 /*
  * Create kernel metadata, open from the kernel tracer and add it to the
  * kernel session.
  */
-int kernel_open_metadata(struct ltt_kernel_session *session, char *path)
+int kernel_open_metadata(struct ltt_kernel_session *session)
 {
 	int ret;
-	struct ltt_kernel_metadata *lkm;
+	struct ltt_kernel_metadata *lkm = NULL;
+
+	assert(session);
 
 	/* Allocate kernel metadata */
-	lkm = trace_kernel_create_metadata(path);
+	lkm = trace_kernel_create_metadata();
 	if (lkm == NULL) {
 		goto error;
 	}
@@ -345,7 +401,7 @@ int kernel_open_metadata(struct ltt_kernel_session *session, char *path)
 	/* Kernel tracer metadata creation */
 	ret = kernctl_open_metadata(session->fd, &lkm->conf->attr);
 	if (ret < 0) {
-		goto error;
+		goto error_open;
 	}
 
 	lkm->fd = ret;
@@ -357,10 +413,12 @@ int kernel_open_metadata(struct ltt_kernel_session *session, char *path)
 
 	session->metadata = lkm;
 
-	DBG("Kernel metadata opened (fd: %d and path: %s)", lkm->fd, lkm->pathname);
+	DBG("Kernel metadata opened (fd: %d)", lkm->fd);
 
 	return 0;
 
+error_open:
+	trace_kernel_destroy_metadata(lkm);
 error:
 	return -1;
 }
@@ -372,6 +430,8 @@ int kernel_start_session(struct ltt_kernel_session *session)
 {
 	int ret;
 
+	assert(session);
+
 	ret = kernctl_start_session(session->fd);
 	if (ret < 0) {
 		PERROR("ioctl start session");
@@ -409,6 +469,8 @@ int kernel_calibrate(int fd, struct lttng_kernel_calibrate *calibrate)
 {
 	int ret;
 
+	assert(calibrate);
+
 	ret = kernctl_calibrate(fd, calibrate);
 	if (ret < 0) {
 		PERROR("calibrate ioctl");
@@ -426,9 +488,11 @@ int kernel_metadata_flush_buffer(int fd)
 {
 	int ret;
 
+	DBG("Kernel flushing metadata buffer on fd %d", fd);
+
 	ret = kernctl_buffer_flush(fd);
 	if (ret < 0) {
-		ERR("Fail to flush metadata buffers %d (ret: %d", fd, ret);
+		ERR("Fail to flush metadata buffers %d (ret: %d)", fd, ret);
 	}
 
 	return 0;
@@ -442,6 +506,8 @@ int kernel_flush_buffer(struct ltt_kernel_channel *channel)
 	int ret;
 	struct ltt_kernel_stream *stream;
 
+	assert(channel);
+
 	DBG("Flush buffer for channel %s", channel->channel->name);
 
 	cds_list_for_each_entry(stream, &channel->stream_list.head, list) {
@@ -464,6 +530,8 @@ int kernel_stop_session(struct ltt_kernel_session *session)
 {
 	int ret;
 
+	assert(session);
+
 	ret = kernctl_stop_session(session->fd);
 	if (ret < 0) {
 		goto error;
@@ -485,13 +553,18 @@ error:
  */
 int kernel_open_channel_stream(struct ltt_kernel_channel *channel)
 {
-	int ret;
+	int ret, count = 0;
 	struct ltt_kernel_stream *lks;
 
+	assert(channel);
+
 	while ((ret = kernctl_create_stream(channel->fd)) >= 0) {
-		lks = trace_kernel_create_stream();
+		lks = trace_kernel_create_stream(channel->channel->name, count);
 		if (lks == NULL) {
-			close(ret);
+			ret = close(ret);
+			if (ret) {
+				PERROR("close");
+			}
 			goto error;
 		}
 
@@ -502,19 +575,18 @@ int kernel_open_channel_stream(struct ltt_kernel_channel *channel)
 			PERROR("fcntl session fd");
 		}
 
-		ret = asprintf(&lks->pathname, "%s/%s_%d",
-				channel->pathname, channel->channel->name, channel->stream_count);
-		if (ret < 0) {
-			PERROR("asprintf kernel create stream");
-			goto error;
-		}
+		lks->tracefile_size = channel->channel->attr.tracefile_size;
+		lks->tracefile_count = channel->channel->attr.tracefile_count;
 
 		/* Add stream to channe stream list */
 		cds_list_add(&lks->list, &channel->stream_list.head);
 		channel->stream_count++;
 
-		DBG("Kernel stream %d created (fd: %d, state: %d, path: %s)",
-				channel->stream_count, lks->fd, lks->state, lks->pathname);
+		/* Increment counter which represent CPU number. */
+		count++;
+
+		DBG("Kernel stream %s created (fd: %d, state: %d)", lks->name, lks->fd,
+				lks->state);
 	}
 
 	return channel->stream_count;
@@ -530,6 +602,8 @@ int kernel_open_metadata_stream(struct ltt_kernel_session *session)
 {
 	int ret;
 
+	assert(session);
+
 	ret = kernctl_create_stream(session->metadata->fd);
 	if (ret < 0) {
 		PERROR("kernel create metadata stream");
@@ -555,13 +629,14 @@ error:
  */
 ssize_t kernel_list_events(int tracer_fd, struct lttng_event **events)
 {
-	int fd, pos;
+	int fd, ret;
 	char *event;
 	size_t nbmem, count = 0;
-	ssize_t size;
 	FILE *fp;
 	struct lttng_event *elist;
 
+	assert(events);
+
 	fd = kernctl_tracepoint_list(tracer_fd);
 	if (fd < 0) {
 		PERROR("kernel tracepoint list");
@@ -580,34 +655,55 @@ ssize_t kernel_list_events(int tracer_fd, struct lttng_event **events)
 	 */
 	nbmem = KERNEL_EVENT_INIT_LIST_SIZE;
 	elist = zmalloc(sizeof(struct lttng_event) * nbmem);
+	if (elist == NULL) {
+		PERROR("alloc list events");
+		count = -ENOMEM;
+		goto end;
+	}
 
-	while ((size = fscanf(fp, "event { name = %m[^;]; };%n\n", &event, &pos)) == 1) {
+	while (fscanf(fp, "event { name = %m[^;]; };\n", &event) == 1) {
 		if (count >= nbmem) {
-			DBG("Reallocating event list from %zu to %zu bytes", nbmem,
-					nbmem * 2);
-			/* Double the size */
-			nbmem <<= 1;
-			elist = realloc(elist, nbmem * sizeof(struct lttng_event));
-			if (elist == NULL) {
+			struct lttng_event *new_elist;
+			size_t new_nbmem;
+
+			new_nbmem = nbmem << 1;
+			DBG("Reallocating event list from %zu to %zu bytes",
+					nbmem, new_nbmem);
+			new_elist = realloc(elist, new_nbmem * sizeof(struct lttng_event));
+			if (new_elist == NULL) {
 				PERROR("realloc list events");
+				free(event);
+				free(elist);
 				count = -ENOMEM;
 				goto end;
 			}
+			/* Zero the new memory */
+			memset(new_elist + nbmem, 0,
+				(new_nbmem - nbmem) * sizeof(struct lttng_event));
+			nbmem = new_nbmem;
+			elist = new_elist;
 		}
 		strncpy(elist[count].name, event, LTTNG_SYMBOL_NAME_LEN);
 		elist[count].name[LTTNG_SYMBOL_NAME_LEN - 1] = '\0';
 		elist[count].enabled = -1;
 		count++;
+		free(event);
 	}
 
 	*events = elist;
 	DBG("Kernel list events done (%zu events)", count);
 end:
-	fclose(fp);	/* closes both fp and fd */
+	ret = fclose(fp);	/* closes both fp and fd */
+	if (ret) {
+		PERROR("fclose");
+	}
 	return count;
 
 error_fp:
-	close(fd);
+	ret = close(fd);
+	if (ret) {
+		PERROR("close");
+	}
 error:
 	return -1;
 }
@@ -619,6 +715,7 @@ int kernel_validate_version(int tracer_fd)
 {
 	int ret;
 	struct lttng_kernel_tracer_version version;
+	struct lttng_kernel_tracer_abi_version abi_version;
 
 	ret = kernctl_tracer_version(tracer_fd, &version);
 	if (ret < 0) {
@@ -627,17 +724,28 @@ int kernel_validate_version(int tracer_fd)
 	}
 
 	/* Validate version */
-	if (version.major != KERN_MODULES_PRE_MAJOR
-		&& version.major != KERN_MODULES_MAJOR) {
+	if (version.major != VERSION_MAJOR) {
+		ERR("Kernel tracer major version (%d) is not compatible with lttng-tools major version (%d)",
+			version.major, VERSION_MAJOR);
 		goto error_version;
 	}
-
-	DBG2("Kernel tracer version validated (major version %d)", version.major);
+	ret = kernctl_tracer_abi_version(tracer_fd, &abi_version);
+	if (ret < 0) {
+		ERR("Failed at getting lttng-modules ABI version");
+		goto error;
+	}
+	if (abi_version.major != LTTNG_MODULES_ABI_MAJOR_VERSION) {
+		ERR("Kernel tracer ABI version (%d.%d) is not compatible with expected ABI major version (%d.*)",
+			abi_version.major, abi_version.minor,
+			LTTNG_MODULES_ABI_MAJOR_VERSION);
+		goto error;
+	}
+	DBG2("Kernel tracer version validated (%d.%d, ABI %d.%d)",
+			version.major, version.minor,
+			abi_version.major, abi_version.minor);
 	return 0;
 
 error_version:
-	ERR("Kernel major version %d is not compatible (supporting <= %d)",
-			version.major, KERN_MODULES_MAJOR)
 	ret = -1;
 
 error:
@@ -669,8 +777,216 @@ int init_kernel_workarounds(void)
 			/* Ignore error, we don't really care */
 		}
 	}
-	fclose(fp);
+	ret = fclose(fp);
+	if (ret) {
+		PERROR("fclose");
+	}
 end_boot_id:
-
 	return 0;
 }
+
+/*
+ * Complete teardown of a kernel session.
+ */
+void kernel_destroy_session(struct ltt_kernel_session *ksess)
+{
+	if (ksess == NULL) {
+		DBG3("No kernel session when tearing down session");
+		return;
+	}
+
+	DBG("Tearing down kernel session");
+
+	/*
+	 * Destroy channels on the consumer if at least one FD has been sent and we
+	 * are in no output mode because the streams are in *no* monitor mode so we
+	 * have to send a command to clean them up or else they leaked.
+	 */
+	if (!ksess->output_traces && ksess->consumer_fds_sent) {
+		int ret;
+		struct consumer_socket *socket;
+		struct lttng_ht_iter iter;
+
+		/* For each consumer socket. */
+		rcu_read_lock();
+		cds_lfht_for_each_entry(ksess->consumer->socks->ht, &iter.iter,
+				socket, node.node) {
+			struct ltt_kernel_channel *chan;
+
+			/* For each channel, ask the consumer to destroy it. */
+			cds_list_for_each_entry(chan, &ksess->channel_list.head, list) {
+				ret = kernel_consumer_destroy_channel(socket, chan);
+				if (ret < 0) {
+					/* Consumer is probably dead. Use next socket. */
+					continue;
+				}
+			}
+		}
+		rcu_read_unlock();
+	}
+
+	/* Close any relayd session */
+	consumer_output_send_destroy_relayd(ksess->consumer);
+
+	trace_kernel_destroy_session(ksess);
+}
+
+/*
+ * Destroy a kernel channel object. It does not do anything on the tracer side.
+ */
+void kernel_destroy_channel(struct ltt_kernel_channel *kchan)
+{
+	struct ltt_kernel_session *ksess = NULL;
+
+	assert(kchan);
+	assert(kchan->channel);
+
+	DBG3("Kernel destroy channel %s", kchan->channel->name);
+
+	/* Update channel count of associated session. */
+	if (kchan->session) {
+		/* Keep pointer reference so we can update it after the destroy. */
+		ksess = kchan->session;
+	}
+
+	trace_kernel_destroy_channel(kchan);
+
+	/*
+	 * At this point the kernel channel is not visible anymore. This is safe
+	 * since in order to work on a visible kernel session, the tracing session
+	 * lock (ltt_session.lock) MUST be acquired.
+	 */
+	if (ksess) {
+		ksess->channel_count--;
+	}
+}
+
+/*
+ * Take a snapshot for a given kernel session.
+ *
+ * Return 0 on success or else return a LTTNG_ERR code.
+ */
+int kernel_snapshot_record(struct ltt_kernel_session *ksess,
+		struct snapshot_output *output, int wait,
+		uint64_t nb_packets_per_stream)
+{
+	int err, ret, saved_metadata_fd;
+	struct consumer_socket *socket;
+	struct lttng_ht_iter iter;
+	struct ltt_kernel_metadata *saved_metadata;
+
+	assert(ksess);
+	assert(ksess->consumer);
+	assert(output);
+
+	DBG("Kernel snapshot record started");
+
+	/* Save current metadata since the following calls will change it. */
+	saved_metadata = ksess->metadata;
+	saved_metadata_fd = ksess->metadata_stream_fd;
+
+	rcu_read_lock();
+
+	ret = kernel_open_metadata(ksess);
+	if (ret < 0) {
+		ret = LTTNG_ERR_KERN_META_FAIL;
+		goto error;
+	}
+
+	ret = kernel_open_metadata_stream(ksess);
+	if (ret < 0) {
+		ret = LTTNG_ERR_KERN_META_FAIL;
+		goto error_open_stream;
+	}
+
+	/* Send metadata to consumer and snapshot everything. */
+	cds_lfht_for_each_entry(ksess->consumer->socks->ht, &iter.iter,
+			socket, node.node) {
+		struct consumer_output *saved_output;
+		struct ltt_kernel_channel *chan;
+
+		/*
+		 * Temporarly switch consumer output for our snapshot output. As long
+		 * as the session lock is taken, this is safe.
+		 */
+		saved_output = ksess->consumer;
+		ksess->consumer = output->consumer;
+
+		pthread_mutex_lock(socket->lock);
+		/* This stream must not be monitored by the consumer. */
+		ret = kernel_consumer_add_metadata(socket, ksess, 0);
+		pthread_mutex_unlock(socket->lock);
+		/* Put back the saved consumer output into the session. */
+		ksess->consumer = saved_output;
+		if (ret < 0) {
+			ret = LTTNG_ERR_KERN_CONSUMER_FAIL;
+			goto error_consumer;
+		}
+
+		/* For each channel, ask the consumer to snapshot it. */
+		cds_list_for_each_entry(chan, &ksess->channel_list.head, list) {
+			pthread_mutex_lock(socket->lock);
+			ret = consumer_snapshot_channel(socket, chan->fd, output, 0,
+					ksess->uid, ksess->gid,
+					DEFAULT_KERNEL_TRACE_DIR, wait,
+					nb_packets_per_stream);
+			pthread_mutex_unlock(socket->lock);
+			if (ret < 0) {
+				ret = LTTNG_ERR_KERN_CONSUMER_FAIL;
+				(void) kernel_consumer_destroy_metadata(socket,
+						ksess->metadata);
+				goto error_consumer;
+			}
+		}
+
+		/* Snapshot metadata, */
+		pthread_mutex_lock(socket->lock);
+		ret = consumer_snapshot_channel(socket, ksess->metadata->fd, output,
+				1, ksess->uid, ksess->gid,
+				DEFAULT_KERNEL_TRACE_DIR, wait, 0);
+		pthread_mutex_unlock(socket->lock);
+		if (ret < 0) {
+			ret = LTTNG_ERR_KERN_CONSUMER_FAIL;
+			goto error_consumer;
+		}
+
+		/*
+		 * The metadata snapshot is done, ask the consumer to destroy it since
+		 * it's not monitored on the consumer side.
+		 */
+		(void) kernel_consumer_destroy_metadata(socket, ksess->metadata);
+	}
+
+	ret = LTTNG_OK;
+
+error_consumer:
+	/* Close newly opened metadata stream. It's now on the consumer side. */
+	err = close(ksess->metadata_stream_fd);
+	if (err < 0) {
+		PERROR("close snapshot kernel");
+	}
+
+error_open_stream:
+	trace_kernel_destroy_metadata(ksess->metadata);
+error:
+	/* Restore metadata state.*/
+	ksess->metadata = saved_metadata;
+	ksess->metadata_stream_fd = saved_metadata_fd;
+
+	rcu_read_unlock();
+	return ret;
+}
+
+/*
+ * Get the syscall mask array from the kernel tracer.
+ *
+ * Return 0 on success else a negative value. In both case, syscall_mask should
+ * be freed.
+ */
+int kernel_syscall_mask(int chan_fd, char **syscall_mask, uint32_t *nr_bits)
+{
+	assert(syscall_mask);
+	assert(nr_bits);
+
+	return kernctl_syscall_mask(chan_fd, syscall_mask, nr_bits);
+}